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<?xml version="1.0" encoding="utf-8" standalone="no"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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<!ENTITY % aptent SYSTEM "apt.ent">
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&apt-author.jgunthorpe;
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<!-- The last update date -->
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<date>29 February 2004</date>
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<refentrytitle>apt.conf</refentrytitle>
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<manvolnum>5</manvolnum>
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<!-- Man page title -->
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<refname>apt.conf</refname>
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<refpurpose>Configuration file for APT</refpurpose>
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<refsect1><title>Description</title>
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<para><filename>apt.conf</filename> is the main configuration file for the APT suite of
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tools, all tools make use of the configuration file and a common command line
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parser to provide a uniform environment. When an APT tool starts up it will
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read the configuration specified by the <envar>APT_CONFIG</envar> environment
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variable (if any) and then read the files in <literal>Dir::Etc::Parts</literal>
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then read the main configuration file specified by
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<literal>Dir::Etc::main</literal> then finally apply the
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command line options to override the configuration directives, possibly
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loading even more config files.</para>
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<para>The configuration file is organized in a tree with options organized into
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functional groups. option specification is given with a double colon
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notation, for instance <literal>APT::Get::Assume-Yes</literal> is an option within
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the APT tool group, for the Get tool. options do not inherit from their
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<para>Syntacticly the configuration language is modeled after what the ISC tools
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such as bind and dhcp use. Lines starting with
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<literal>//</literal> are treated as comments (ignored).
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Each line is of the form
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<literal>APT::Get::Assume-Yes "true";</literal> The trailing
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semicolon is required and the quotes are optional. A new scope can be
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opened with curly braces, like:</para>
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<informalexample><programlisting>
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</programlisting></informalexample>
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<para>with newlines placed to make it more readable. Lists can be created by
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opening a scope and including a single word enclosed in quotes followed by a
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semicolon. Multiple entries can be included, each separated by a semicolon.</para>
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<informalexample><programlisting>
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DPkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt";};
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</programlisting></informalexample>
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<para>In general the sample configuration file in
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<filename>&docdir;examples/apt.conf</filename> &configureindex;
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is a good guide for how it should look.</para>
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<para>Two specials are allowed, <literal>#include</literal> and <literal>#clear</literal>
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<literal>#include</literal> will include the given file, unless the filename
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ends in a slash, then the whole directory is included.
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<literal>#clear</literal> is used to erase a list of names.</para>
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<para>All of the APT tools take a -o option which allows an arbitrary configuration
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directive to be specified on the command line. The syntax is a full option
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name (<literal>APT::Get::Assume-Yes</literal> for instance) followed by an equals
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sign then the new value of the option. Lists can be appended too by adding
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a trailing :: to the list name.</para>
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<refsect1><title>The APT Group</title>
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<para>This group of options controls general APT behavior as well as holding the
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options for all of the tools.</para>
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<varlistentry><term>Architecture</term>
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<listitem><para>System Architecture; sets the architecture to use when fetching files and
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parsing package lists. The internal default is the architecture apt was
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compiled for.</para></listitem>
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<varlistentry><term>Ignore-Hold</term>
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<listitem><para>Ignore Held packages; This global option causes the problem resolver to
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ignore held packages in its decision making.</para></listitem>
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<varlistentry><term>Clean-Installed</term>
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<listitem><para>Defaults to on. When turned on the autoclean feature will remove any packages
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which can no longer be downloaded from the cache. If turned off then
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packages that are locally installed are also excluded from cleaning - but
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note that APT provides no direct means to reinstall them.</para></listitem>
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<varlistentry><term>Immediate-Configure</term>
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<listitem><para>Disable Immediate Configuration; This dangerous option disables some
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of APT's ordering code to cause it to make fewer dpkg calls. Doing
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so may be necessary on some extremely slow single user systems but
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is very dangerous and may cause package install scripts to fail or worse.
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Use at your own risk.</para></listitem>
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<varlistentry><term>Force-LoopBreak</term>
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<listitem><para>Never Enable this option unless you -really- know what you are doing. It
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permits APT to temporarily remove an essential package to break a
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Conflicts/Conflicts or Conflicts/Pre-Depend loop between two essential
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packages. SUCH A LOOP SHOULD NEVER EXIST AND IS A GRAVE BUG. This option
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will work if the essential packages are not tar, gzip, libc, dpkg, bash or
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anything that those packages depend on.</para></listitem>
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<varlistentry><term>Cache-Limit</term>
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<listitem><para>APT uses a fixed size memory mapped cache file to store the 'available'
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information. This sets the size of that cache (in bytes).</para></listitem>
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<varlistentry><term>Build-Essential</term>
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<listitem><para>Defines which package(s) are considered essential build dependencies.</para></listitem>
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<varlistentry><term>Get</term>
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<listitem><para>The Get subsection controls the &apt-get; tool, please see its
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documentation for more information about the options here.</para></listitem>
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<varlistentry><term>Cache</term>
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<listitem><para>The Cache subsection controls the &apt-cache; tool, please see its
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documentation for more information about the options here.</para></listitem>
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<varlistentry><term>CDROM</term>
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<listitem><para>The CDROM subsection controls the &apt-cdrom; tool, please see its
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documentation for more information about the options here.</para></listitem>
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<refsect1><title>The Acquire Group</title>
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<para>The <literal>Acquire</literal> group of options controls the download of packages
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and the URI handlers.
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<varlistentry><term>Queue-Mode</term>
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<listitem><para>Queuing mode; <literal>Queue-Mode</literal> can be one of <literal>host</literal> or
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<literal>access</literal> which determines how APT parallelizes outgoing
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connections. <literal>host</literal> means that one connection per target host
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will be opened, <literal>access</literal> means that one connection per URI type
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will be opened.</para></listitem>
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<varlistentry><term>Retries</term>
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<listitem><para>Number of retries to perform. If this is non-zero APT will retry failed
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files the given number of times.</para></listitem>
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<varlistentry><term>Source-Symlinks</term>
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<listitem><para>Use symlinks for source archives. If set to true then source archives will
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be symlinked when possible instead of copying. True is the default.</para></listitem>
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<varlistentry><term>http</term>
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<listitem><para>HTTP URIs; http::Proxy is the default http proxy to use. It is in the
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standard form of <literal>http://[[user][:pass]@]host[:port]/</literal>. Per
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host proxies can also be specified by using the form
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<literal>http::Proxy::<host></literal> with the special keyword <literal>DIRECT</literal>
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meaning to use no proxies. The <envar>http_proxy</envar> environment variable
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will override all settings.</para>
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<para>Three settings are provided for cache control with HTTP/1.1 compliant
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proxy caches. <literal>No-Cache</literal> tells the proxy to not use its cached
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response under any circumstances, <literal>Max-Age</literal> is sent only for
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index files and tells the cache to refresh its object if it is older than
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the given number of seconds. Debian updates its index files daily so the
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default is 1 day. <literal>No-Store</literal> specifies that the cache should never
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store this request, it is only set for archive files. This may be useful
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to prevent polluting a proxy cache with very large .deb files. Note:
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Squid 2.0.2 does not support any of these options.</para>
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<para>The option <literal>timeout</literal> sets the timeout timer used by the method,
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this applies to all things including connection timeout and data timeout.</para>
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<para>One setting is provided to control the pipeline depth in cases where the
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remote server is not RFC conforming or buggy (such as Squid 2.0.2)
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<literal>Acquire::http::Pipeline-Depth</literal> can be a value from 0 to 5
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indicating how many outstanding requests APT should send. A value of
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zero MUST be specified if the remote host does not properly linger
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on TCP connections - otherwise data corruption will occur. Hosts which
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require this are in violation of RFC 2068.</para></listitem>
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<varlistentry><term>ftp</term>
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<listitem><para>FTP URIs; ftp::Proxy is the default proxy server to use. It is in the
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standard form of <literal>ftp://[[user][:pass]@]host[:port]/</literal> and is
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overridden by the <envar>ftp_proxy</envar> environment variable. To use a ftp
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proxy you will have to set the <literal>ftp::ProxyLogin</literal> script in the
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configuration file. This entry specifies the commands to send to tell
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the proxy server what to connect to. Please see
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&configureindex; for an example of
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how to do this. The subsitution variables available are
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<literal>$(PROXY_USER)</literal> <literal>$(PROXY_PASS)</literal> <literal>$(SITE_USER)</literal>
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<literal>$(SITE_PASS)</literal> <literal>$(SITE)</literal> and <literal>$(SITE_PORT)</literal>
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Each is taken from it's respective URI component.</para>
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<para>The option <literal>timeout</literal> sets the timeout timer used by the method,
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this applies to all things including connection timeout and data timeout.</para>
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<para>Several settings are provided to control passive mode. Generally it is
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safe to leave passive mode on, it works in nearly every environment.
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However some situations require that passive mode be disabled and port
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mode ftp used instead. This can be done globally, for connections that
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go through a proxy or for a specific host (See the sample config file
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for examples).</para>
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<para>It is possible to proxy FTP over HTTP by setting the <envar>ftp_proxy</envar>
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environment variable to a http url - see the discussion of the http method
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above for syntax. You cannot set this in the configuration file and it is
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not recommended to use FTP over HTTP due to its low efficiency.</para>
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<para>The setting <literal>ForceExtended</literal> controls the use of RFC2428
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<literal>EPSV</literal> and <literal>EPRT</literal> commands. The defaut is false, which means
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these commands are only used if the control connection is IPv6. Setting this
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to true forces their use even on IPv4 connections. Note that most FTP servers
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do not support RFC2428.</para></listitem>
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<varlistentry><term>cdrom</term>
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<listitem><para>CDROM URIs; the only setting for CDROM URIs is the mount point,
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<literal>cdrom::Mount</literal> which must be the mount point for the CDROM drive
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as specified in <filename>/etc/fstab</filename>. It is possible to provide
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alternate mount and unmount commands if your mount point cannot be listed
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in the fstab (such as an SMB mount and old mount packages). The syntax
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is to put <literallayout>"/cdrom/"::Mount "foo";</literallayout> within
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the cdrom block. It is important to have the trailing slash. Unmount
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commands can be specified using UMount.</para></listitem>
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<varlistentry><term>gpgv</term>
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<listitem><para>GPGV URIs; the only option for GPGV URIs is the option to pass additional parameters to gpgv.
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<literal>gpgv::Options</literal> Additional options passed to gpgv.
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<refsect1><title>Directories</title>
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<para>The <literal>Dir::State</literal> section has directories that pertain to local
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state information. <literal>lists</literal> is the directory to place downloaded
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package lists in and <literal>status</literal> is the name of the dpkg status file.
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<literal>preferences</literal> is the name of the APT preferences file.
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<literal>Dir::State</literal> contains the default directory to prefix on all sub
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items if they do not start with <filename>/</filename> or <filename>./</filename>.</para>
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<para><literal>Dir::Cache</literal> contains locations pertaining to local cache
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information, such as the two package caches <literal>srcpkgcache</literal> and
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<literal>pkgcache</literal> as well as the location to place downloaded archives,
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<literal>Dir::Cache::archives</literal>. Generation of caches can be turned off
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by setting their names to be blank. This will slow down startup but
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save disk space. It is probably prefered to turn off the pkgcache rather
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than the srcpkgcache. Like <literal>Dir::State</literal> the default
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directory is contained in <literal>Dir::Cache</literal></para>
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<para><literal>Dir::Etc</literal> contains the location of configuration files,
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<literal>sourcelist</literal> gives the location of the sourcelist and
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<literal>main</literal> is the default configuration file (setting has no effect,
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unless it is done from the config file specified by
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<envar>APT_CONFIG</envar>.</para>
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<para>The <literal>Dir::Parts</literal> setting reads in all the config fragments in
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lexical order from the directory specified. After this is done then the
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main config file is loaded.</para>
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<para>Binary programs are pointed to by <literal>Dir::Bin</literal>. <literal>Dir::Bin::Methods</literal>
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specifies the location of the method handlers and <literal>gzip</literal>,
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<literal>dpkg</literal>, <literal>apt-get</literal> <literal>dpkg-source</literal>
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<literal>dpkg-buildpackage</literal> and <literal>apt-cache</literal> specify the location
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of the respective programs.</para>
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<refsect1><title>APT in DSelect</title>
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When APT is used as a &dselect; method several configuration directives
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control the default behaviour. These are in the <literal>DSelect</literal> section.</para>
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<varlistentry><term>Clean</term>
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<listitem><para>Cache Clean mode; this value may be one of always, prompt, auto,
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pre-auto and never. always and prompt will remove all packages from
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the cache after upgrading, prompt (the default) does so conditionally.
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auto removes only those packages which are no longer downloadable
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(replaced with a new version for instance). pre-auto performs this
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action before downloading new packages.</para></listitem>
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<varlistentry><term>options</term>
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<listitem><para>The contents of this variable is passed to &apt-get; as command line
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options when it is run for the install phase.</para></listitem>
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<varlistentry><term>Updateoptions</term>
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<listitem><para>The contents of this variable is passed to &apt-get; as command line
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options when it is run for the update phase.</para></listitem>
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<varlistentry><term>PromptAfterUpdate</term>
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<listitem><para>If true the [U]pdate operation in &dselect; will always prompt to continue.
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The default is to prompt only on error.</para></listitem>
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<refsect1><title>How APT calls dpkg</title>
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<para>Several configuration directives control how APT invokes &dpkg;. These are
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in the <literal>DPkg</literal> section.</para>
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<varlistentry><term>options</term>
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<listitem><para>This is a list of options to pass to dpkg. The options must be specified
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using the list notation and each list item is passed as a single argument
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to &dpkg;.</para></listitem>
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<varlistentry><term>Pre-Invoke</term><term>Post-Invoke</term>
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<listitem><para>This is a list of shell commands to run before/after invoking &dpkg;.
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Like <literal>options</literal> this must be specified in list notation. The
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commands are invoked in order using <filename>/bin/sh</filename>, should any
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fail APT will abort.</para></listitem>
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<varlistentry><term>Pre-Install-Pkgs</term>
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<listitem><para>This is a list of shell commands to run before invoking dpkg. Like
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<literal>options</literal> this must be specified in list notation. The commands
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are invoked in order using <filename>/bin/sh</filename>, should any fail APT
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will abort. APT will pass to the commands on standard input the
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filenames of all .deb files it is going to install, one per line.</para>
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<para>Version 2 of this protocol dumps more information, including the
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protocol version, the APT configuration space and the packages, files
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and versions being changed. Version 2 is enabled by setting
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<literal>DPkg::Tools::options::cmd::Version</literal> to 2. <literal>cmd</literal> is a
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command given to <literal>Pre-Install-Pkgs</literal>.</para></listitem>
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<varlistentry><term>Run-Directory</term>
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<listitem><para>APT chdirs to this directory before invoking dpkg, the default is
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<filename>/</filename>.</para></listitem>
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<varlistentry><term>Build-options</term>
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<listitem><para>These options are passed to &dpkg-buildpackage; when compiling packages,
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the default is to disable signing and produce all binaries.</para></listitem>
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<refsect1><title>Debug options</title>
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<para>Most of the options in the <literal>debug</literal> section are not interesting to
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the normal user, however <literal>Debug::pkgProblemResolver</literal> shows
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interesting output about the decisions dist-upgrade makes.
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<literal>Debug::NoLocking</literal> disables file locking so APT can do some
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operations as non-root and <literal>Debug::pkgDPkgPM</literal> will print out the
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command line for each dpkg invokation. <literal>Debug::IdentCdrom</literal> will
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disable the inclusion of statfs data in CDROM IDs.
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<literal>Debug::Acquire::gpgv</literal> Debugging of the gpgv method.
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<refsect1><title>Examples</title>
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<para>&configureindex; is a
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configuration file showing example values for all possible
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<refsect1><title>Files</title>
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<para><filename>/etc/apt/apt.conf</filename></para>
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<refsect1><title>See Also</title>
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<para>&apt-cache;, &apt-config;<!-- ? reading apt.conf -->, &apt-preferences;.</para>
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doc/apt.conf.5.xml
